U.S. patent application number 10/491789 was filed with the patent office on 2004-10-07 for signal repeating device.
Invention is credited to Tanabe, Shinji.
Application Number | 20040198075 10/491789 |
Document ID | / |
Family ID | 27678026 |
Filed Date | 2004-10-07 |
United States Patent
Application |
20040198075 |
Kind Code |
A1 |
Tanabe, Shinji |
October 7, 2004 |
Signal repeating device
Abstract
A communication equipment includes short-circuited stubs
electrically connecting signal through holes to ground through
holes, respectively. Thus, it reduces signal reflection even if the
transmission speed of a signal is increased.
Inventors: |
Tanabe, Shinji; (Tokyo,
JP) |
Correspondence
Address: |
LEYDIG VOIT & MAYER, LTD
700 THIRTEENTH ST. NW
SUITE 300
WASHINGTON
DC
20005-3960
US
|
Family ID: |
27678026 |
Appl. No.: |
10/491789 |
Filed: |
April 6, 2004 |
PCT Filed: |
February 12, 2003 |
PCT NO: |
PCT/JP03/01446 |
Current U.S.
Class: |
439/65 |
Current CPC
Class: |
H05K 1/0219 20130101;
H05K 3/308 20130101; H05K 1/14 20130101; H05K 2201/09627 20130101;
H01P 5/02 20130101; H05K 3/366 20130101; H05K 2201/10189 20130101;
H05K 3/3447 20130101; H05K 2201/09609 20130101; H05K 1/0251
20130101; H05K 1/0222 20130101; H05K 3/429 20130101; H05K 1/115
20130101 |
Class at
Publication: |
439/065 |
International
Class: |
H01R 012/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 12, 2002 |
JP |
2002-034422 |
Claims
1. A communication equipment comprising a signal transmitting
section for electrically connecting a first transmission path, that
is connected to a signal through hole in a first boards to a second
transmission paths that is connected to a signal through hole in a
second board, wherein the signal through holes in the first and
second boards are each connected to respective electrically
short-circuited stubs.
2. The communication equipment according to claim 1, wherein the
short-circuited stubs respectively electrically connect the signal
through holes to ground through holes that are connected to a
ground.
3. The communication equipment according to claim 1, wherein the
signal transmitting section has a characteristic impedance larger
than characteristic impedance of the first and second transmissions
paths of the first and second boards.
4. The communication equipment according to claim 1, wherein the
signal transmitting section comprises a first connector having a
first connector pin inserted into the signal through hole of the
first board and a second connector pin inserted into the signal
through hole of the second board; and a second connector having a
first connector pin inserted into a ground through hole of the
first board and a second connector pin inserted into a ground
through hole of the second board.
5. The communication equipment according to claim 1, wherein the
second board consists of an LSI, the signal transmitting section is
a package that incorporates the LSI and electrically connects the
transmission path of the first board to a pin of the LSI.
6. The communication equipment according to claim 1, wherein a
connecting position of the short-circuited stub to the first
transmission path is determined considering admittance of said
signal transmitting section, characteristic admittance of the first
transmission path of the first board, input admittance seen by
looking into the signal transmitting section from the first
transmission path of the first board, and a phase constant.
7. The communication equipment according to claim 1, wherein length
of one of the short-circuited stubs is determined considering
characteristic admittance of the transmission path of the first
board, input admittance seen by looking into the signal
transmitting section from the first transmission path of the first
board, and a phase constant.
8. The communication equipment according to claim 2, wherein when
locating a plurality of signal through holes and a plurality of
ground through holes in at least one of the first and second
boards, the connecting position of the short circuited stubs is
determined considering admittance of the signal transmitting
section, characteristic admittance of the first transmission path
of the first board, input admittance seen by looking into the
signal transmitting section from the first transmission path of the
first board, and a phase constant; the length of one of the
short-circuited stubs is determined considering the characteristic
admittance of the first transmission path of the first board, the
input admittance seen by looking into the signal transmitting
section from the first transmission path of the first board, and
the phase constant; and the signal through holes and the ground
through holes are disposed alternately at regular intervals in at
least one of the first and second boards.
Description
TECHNICAL FIELD
[0001] The present invention relates to a stub structure for
preventing signal reflection that will occur when transmitting a
signal from a first board to a second board.
BACKGROUND ART
[0002] FIG. 1 is a diagram showing a configuration of a
conventional board connection on a transmission line disclosed in
Japanese patent application laid-open No. 4-28182/1992, for
example. In FIG. 1, the reference numeral 1 designates a daughter
card; 2 designates a transmission path of the daughter card 1; 3
designates a signal through hole (through hole used for a signal)
of the daughter card 1; 4 designates a ground layer; 5 designates a
ground through hole (through hole used for a ground) of the
daughter card 1; 6 designates a backplane; 7 designates a
transmission path of the backplane 6; 8 designates a signal through
hole of the backplane 6; 9 designates a ground layer; 10 designates
a ground through hole of the backplane 6; 11 designates a connector
having its connector pin 11a inserted into the signal through hole
3 of the daughter card 1 and its connector pin 11b inserted into
the signal through hole 8 of the backplane 6; and 12 designates a
connector having its connector pin 12a inserted into the ground
through hole 5 of the daughter card 1, and its connector pin 12b
inserted into the ground through hole 10 of the backplane 6.
[0003] Next, the operation will be described.
[0004] The connector pin 11a of the connector 11 is inserted into
the signal through hole 3 of the daughter card 1, and the connector
pin 11b of the connector 11 is inserted into the through hole 8 of
the backplane 6.
[0005] Thus, the transmission path 2 of the daughter card 1 is
electrically connected to the transmission path 7 of the backplane
6.
[0006] Accordingly, a signal output from a driver or the like
installed in the daughter card 1 is transmitted from the
transmission path 2 of the daughter card 1 to the transmission path
7 of the backplane 6 via the connector 11.
[0007] However, if the characteristic impedance of the transmission
path 2 of the daughter card 1 differs from that of the transmission
path 7 of the backplane 6, the impedance mismatching will bring
about signal reflection, which prevents high-speed transmission of
the signal.
[0008] In view of this, to minimize the signal reflection due to
the impedance mismatching, the conventional transmission lines make
a contrivance as to the placement of the ground and reducing the
length of the fitting portion of the connector 11.
[0009] With the foregoing arrangement, the conventional
communication equipment can control the signal reflection as long
as the transmission speed of the signal is within a certain limit.
However, as the transmission speed of the signal further increases,
a problem arises of being unable to control signal reflection
sufficiently by only contriving the placement of the ground and the
length of the fitting portion of the connector 11.
[0010] The present invention is implemented to solve the foregoing
problem. Therefore it is an object of the present invention to
provide a stub line for controlling the signal reflection even if
the transmission speed of the signal is increased.
DISCLOSURE OF THE INVENTION
[0011] The signal transmitter in accordance with the present
invention includes electrical short stubs connected to signal
through holes in first and second boards.
[0012] This offers an advantage of being able to control the signal
reflection even if the transmission speed of the signal is
increased.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a diagram showing a configuration of conventional
communication equipment;
[0014] FIG. 2 is a diagram showing a configuration of an embodiment
1 of the signal transmitter in accordance with the present
invention;
[0015] FIG. 3 is an enlarged perspective view of a backplane of the
equipment of FIG. 2;
[0016] FIG. 4 is a diagram illustrating an admittance diagram
(Smith chart);
[0017] FIG. 5 is a view showing a configuration of an embodiment 2
of the communication equipment in accordance with the present
invention;
[0018] FIG. 6(a) is a plane view showing a layout of through holes,
and FIG. 6(b) is a cross-sectional view of some of the through
holes; and
[0019] FIG. 7(a) is a plane view showing a layout of through holes,
and FIG. 7(b) is a cross-sectional view of some of the through
holes.
BEST MODE FOR CARRYING OUT THE INVENTION
[0020] The best mode for carrying out the invention will now be
described with reference to the accompanying drawings to explain
the present invention in more detail.
EMBODIMENT 1
[0021] FIG. 2 is a diagram showing a configuration of an embodiment
1 of the communication equipment in accordance with the present
invention; and FIG. 3 is an enlarged perspective view of a
backplane of the equipment of FIG. 2. In FIG. 2, the reference
numeral 1 designates a daughter card (first board); 2 designates a
transmission path of the daughter card 1; 3 designates a signal
through hole (through hole used for a signal) of the daughter card
1; 4 designates a ground layer; 5 designates a ground through hole
(through hole used for a ground) of the daughter card 1; 6
designates a backplane (second board); 7 designates a transmission
path of the backplane 6; 8 designates a signal through hole of the
backplane 6; 9 designates a ground layer; and 10 designates a
ground through hole of the backplane 6.
[0022] The reference numeral 11 designates a connector (first
connector) having its connector pin 11a inserted into the signal
through hole 3 of the daughter card 1 and its connector pin 11b
inserted into the signal through hole 8 of the backplane 6; and 12
designates a connector (second connector) having its connector pin
12a inserted into the ground through hole 5 of the daughter card 1,
and its connector pin 12b inserted into the ground through hole 10
of the backplane 6. The connectors 11 and 12 constitute
transmission lines.
[0023] The reference numeral 13 designates a short stub for
electrically connecting the signal through hole 3 with the ground
through hole 5, and 14 designates a short stub for electrically
connecting the signal through hole 8 with the ground through hole
10.
[0024] Next, the operation will be described.
[0025] The connector pin 11a of the connector 11 is inserted into
the signal through hole 3 of the daughter card 1, and the connector
pin 11b of the connector 11 is inserted into the through hole 8 of
the backplane 6.
[0026] Thus, the transmission path 2 of the daughter card 1 is
electrically connected to the transmission path 7 of the backplane
6.
[0027] Accordingly, a signal output from a driver or the like
installed in the daughter card 1 is transmitted from the
transmission path 2 of the daughter card 1 to the transmission path
7 of the backplane 6 via the connector 11.
[0028] However, if the characteristic impedance of the transmission
path 2 of the daughter card 1 differs from that of the transmission
path 7 of the backplane 6, the impedance mismatching will bring
about signal reflection, which prevents high-speed transmission of
the signal.
[0029] In view of this, to control the signal reflection, the
present embodiment 1 has the electrical short stub 13 connected to
the signal through hole 3 of the daughter card 1, and the
electrical short stub 14 connected to the signal through hole 8 of
the backplane 6.
[0030] In other words, the signal through hole 3 is electrically
connected to the ground through hole 5 by the short stub 13 in the
daughter card 1, and the signal through hole 8 is electrically
connected to the ground through hole 10 by the short stub 14 in the
backplane 6.
[0031] Here, the connecting position 11 of the short stub 13 to the
transmission path is determined such that the normalized
conductance g, which is obtained by dividing the imaginary
component of the input admittance Y.sub.i by the characteristic
admittance Y.sub.0 (=1/Z.sub.0) of the transmission path 2, becomes
"1". Here, the input admittance Y.sub.i is defined as the
admittance seen by looking into the load side, the connector 11,
from the signal source side, the daughter card 1.
[0032] More specifically, as illustrated in the admittance diagram
(Smith chart) of FIG. 4, considering that the input impedance of
the connector 11 equals the load impedance Z.sub.L, its admittance
point is denoted by A1 in FIG. 4.
[0033] Here, considering that the ground through hole 5 is
inductive, a condition is set such that the load impedance Z.sub.L
(characteristic impedance) of the connector 11 becomes greater than
the characteristic impedance of the transmission path 2 of the
daughter card 1. Then, the position of the standing wave moves so
that the distance from the tip of the connector pin 11a to the
connecting position of the short stub 13 to the transmission path
can be sharply reduced to about {fraction (1/10)} of the
wavelength. Thus, the admittance point is moved from A1 to A1' by
setting the load impedance of the connector 11 such that the
foregoing condition is satisfied. In this case, the short stub 13
can be fixed to the ground through hole 5 directly.
[0034] Next, a decision is made such that the normalized
conductance g becomes "1", which is obtained by dividing the
imaginary component of the input admittance Y.sub.i seen by looking
into the connector 11 from the daughter card 1 side by the
characteristic admittance Y.sub.0 (=1/Z.sub.0) of the transmission
path 2. Thus, the admittance point is moved from A1' to A2 on a
curve on which g=1.
[0035] Subsequently, a condition is set such that the length of the
short stub 13 matches the ratio between the characteristic
impedance (characteristic admittance) of the short stub 13 and the
input reactance (susceptance) of the short stub 13. Then, the
inductance of the short stub 13 and the capacitance of the line
(line from the tip of the connector pin 11a to the connecting
position of the short stub 13) have their susceptance components
canceled each other. Accordingly, the admittance point is moved
from A2 to A3, the origin of the Smith chart, by setting the length
of the short stub 13 such that it meets the foregoing condition.
Thus, the impedance matching is achieved.
[0036] Incidentally, when the backplane 6 is a signal source, the
short stub 14 is provided, which electrically connects the signal
through hole 8 to the ground through hole 10. In this case, the
connecting position l.sub.2 of the short stub 14 is determined in
the same manner as that of the short stub 13. In other words, it is
determined such that the normalized conductance g becomes "1",
which is, obtained by dividing the imaginary component of the input
admittance Y.sub.i seen by looking into the load side, the
connector 11, from the signal source, the backplane 6 side, by the
characteristic admittance Y.sub.0 (=1/Z.sub.0) of the transmission
path 7.
[0037] As described above, the present embodiment 1 is configured
such that it comprises the short stub 13 or 14 for electrically
connecting the signal through hole 3 or 8 to the ground through
hole 5 or 10, respectively. Thus, the present embodiment 1 offers
an advantage of being able to control the signal reflection even if
the transmission speed of the signal is increased.
[0038] Specifically, it can improve the S/N, jitter and error rate
of the device because the signal energy on the transmission path is
transmitted to the final stage or another side receiver without
loss.
[0039] Furthermore, the present embodiment 1 is configured such
that it sets the load impedance Z.sub.L of the connector 11 greater
than the characteristic impedance of the transmission path 2 of the
daughter card 1. Thus, the present embodiment 1 offers an advantage
of being able to reduce the distance from the tip of the connector
pin 11a to the connecting position of the short stub 13 to about
{fraction (1/10)} of the wavelength.
EMBODIMENT 2
[0040] FIG. 5 is a view showing a configuration of an embodiment 2
of the package in accordance with the present invention. In FIG. 5,
the same reference numerals designate the same or like portions to
those of FIG. 2, and their description will be omitted here.
[0041] In FIG. 5, the reference numeral 21 designates a printed
circuit board on which an LSI 23 is mounted, 22 designates a ball,
23 designates the LSI corresponding to a board (second board) on a
signal receiving side, and 24 designates bonding wires electrically
connecting the ball 22 with the pins of the LSI 23. The printed
circuit board 21, balls 22 and bonding wires 24 constitute a
package.
[0042] Although the signal transmitting section consists of the
connectors 11 and 12 in the foregoing embodiment 1, it may consists
of the package electrically connecting the transmission path 2 of
the board on the signal transmitting side with the pins of the LSI
23 mounted on the package as shown in FIG. 5.
[0043] In this case, the connecting position l.sub.m and length
l.sub.s of the short stub 13 are determined such that the inductive
susceptance (reactance), the imaginary part of the admittance
(impedance), of the short stub 13 is canceled by the capacitive
susceptance (reactance), the imaginary part of the admittance
(impedance), seen by looking into the LSI 23 side from the
connecting position of the short stub 13.
[0044] More specifically, the connecting position l.sub.m of the
short stub 13 is determined such that the normalized conductance g,
which is obtained by dividing the imaginary component of the input
admittance Y.sub.i seen by looking into the LSI 23 from the signal
transmitting side by the characteristic admittance Y.sub.0
(=1/Z.sub.0) of the transmission path 2, becomes "1" by using a
Smith chart, or the following expression (1).
Y.sub.i=Y.sub.0(Y.sub.L cos .beta.l.sub.m+jY.sub.0 sin
.beta.l.sub.m)/(Y.sub.0 cos .beta.l.sub.m+jY.sub.L sin
.beta.l.sub.m) (1)
1/Y.sub.0=Z.sub.0=(.eta./.pi.)cos h.sup.-1(d/.phi.) (2)
[0045] where
[0046] .beta.: phase constant (.beta.=.omega./.lambda.);
[0047] Y.sub.L: admittance of the signal transmission line;
[0048] .eta.: wave impedance in free space;
[0049] .phi.: diameter of the through holes 3 and 5; and
[0050] d: distance between the signal through hole 3 and ground
through hole 5.
[0051] On the other hand, the length l.sub.s of the short stub 13
is obtained such that when the susceptance seen by looking into the
LSI 23 from the connecting position of the short stub 13 l.sub.m is
B[S], the susceptance seen by looking into the short connected side
of the short stub 13 from the connecting position l.sub.m of the
short stub 13 becomes -B[S] by using a Smith chart or the following
expression (3). The following expression (3) is obtained by placing
the admittance Y.sub.L of the signal transmitting section in the
foregoing expression (1) at infinity (.infin.:
short-circuited).
Y.sub.i=-jY.sub.0 cos .beta.l.sub.s (3)
[0052] As described above, the present embodiment 2 is configured
such that the signal transmitting section consists of the package
electrically connecting the transmission path 2 of the board on the
signal transmitting side with the pins of the LSI 23 mounted on the
package. Thus, the present embodiment 2 offers an advantage of
being able to control the signal reflection even if the package is
used as the signal transmitting section.
[0053] In addition, the present embodiment 2 is configured such
that the connecting position l.sub.m of the short stub 13 is
determined considering the admittance Y.sub.L of the signal
transmitting section, the characteristic admittance Y.sub.0 of the
transmission path 2 of the board, the input admittance Y.sub.i seen
by looking into the signal transmitting section from the
transmission path of the board, and the phase constant .beta..
Accordingly, the present embodiment 2 offers an advantage of being
able to control the signal reflection, even if the transmission
speed of the signal is increased.
[0054] Furthermore, the present embodiment 2 is configured such
that the length l.sub.s of the short stub 13 is determined
considering the characteristic admittance Y.sub.0 of the
transmission path 2 of the board, the input admittance Y.sub.i seen
by looking into the signal transmitting section from the
transmission path of the board, and the phase constant .beta..
Accordingly, the present embodiment 2 offers an advantage of being
able to control the signal reflection, even if the transmission
speed of the signal is increased.
EMBODIMENT 3
[0055] Although the foregoing embodiment 1 is described by way of
example including a single signal through hole 3 and ground through
hole 5 placed in the daughter card 1, a plurality of signal through
holes 3 and ground through holes 5 can be placed in the daughter
card 1. In this case, the signal through holes 3 and ground through
holes 5 can be disposed alternately at regular intervals as shown
in FIG. 6.
[0056] Here, the connecting position l.sub.m of the short stub 13
is determined by the foregoing expression (1), and the length
l.sub.s of the short stub 13 is determined by using the foregoing
expression (3) or the Smith chart of FIG. 4.
[0057] Thus, the present embodiment 3 offers an advantage of being
able to determine the connecting position l.sub.m and length
l.sub.s of the short stub 13 flexibly over a wide range.
EMBODIMENT 4
[0058] The foregoing embodiment 3 is described by way of example
including signal through holes 3 and ground through holes 5
disposed alternately at regular intervals. However, when
transmitting a signal from the backplane 6 to the daughter card 1,
signal through holes 8 and ground through holes 10 can be disposed
alternately at regular intervals as shown in FIG. 7.
[0059] Here, the connecting position l.sub.m of the short stub 14
is determined by the foregoing expression (1), and the length
l.sub.s of the short stub 14 is determined by using the foregoing
expression (3) or the Smith chart of FIG. 4.
[0060] Thus, the present embodiment 4 offers an advantage of being
able to determine the connecting position l.sub.m and length
l.sub.s of the short stub 14 flexibly over a wide range.
[0061] Industrial Applicability
[0062] As described above, the communication equipment in
accordance with the present invention is applicable to reducing the
signal reflection as much as possible which occurs when
transmitting a signal from a first board to a second board that are
connected with each other.
* * * * *